Li-N₂ Battery for Ammonia Synthesis and Computational Insight

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• The Haber-Bosch process dominates ammonia synthesis but relies on fossil fuels.
• Lithium-mediated nitrogen reduction (LiNR) is a promising alternative, but its mechanisms remain unclear.
• Continuous LiNR (C-LiNR) has been reported, yet internal reactions require further elucidation.

Purpose of the Study:

• To propose and investigate an intermittent lithium-mediated nitrogen reduction for ammonia synthesis (I-LiNR) to clarify LiNR mechanisms.
• To demonstrate a method for synthesizing ammonia in a separate, understandable process.
• To explore the potential of Li-N₂ batteries for ammonia production.

Main Methods:

• Development of an intermittent LiNR process within the cathode chamber of a Li-N₂ battery.
• Experimental detection of reaction products including Li₃N, LiOH, and NH₃.
• Density functional theory (DFT) calculations to investigate reaction mechanisms and lithium's role in dinitrogen activation.

Main Results:

• Successful demonstration of I-LiNR through distinct discharge, stand, and charge steps (N₂ lithification, protonation, lithium regeneration).
• Experimental validation of a reaction pathway with detected ammonia and intermediate products.
• DFT calculations provided insights into the Li-N₂ battery mechanism, Li-mediated ammonia synthesis, and LiOH decomposition.

Conclusions:

• I-LiNR provides a viable pathway for understanding LiNR mechanisms and offers a quasi-continuous ammonia synthesis method.
• The study highlights lithium's crucial role in activating dinitrogen for ammonia synthesis.
• Findings expand the scope of LiOH-based batteries and suggest a research direction from Li-air to Li-N₂ systems.